Electric condenser



Nov. 11, 1930. E- T, HOCH 1,780,917

ELECTRIC CONDENSER Filed May 29, 192

Patented Nov. 11p,

UNITED srA111515 PATENT oFFlcE ELLEEY T. Hoon, E BLQMEIELD, NEW JERSEY, AssmNoR To BELL TELEPHONE LABORATORIES, INCORPORATED, YORK 0E 'NEW Y'oEx, N. Y.,

` ELECTRIC coNnENsEn A Co'RPonATIoN or NEW Application sled may 29, i926. serial No. 112,422.

This invention relates to condensers and more especially to what are commonly known as paper condensers. 1

The so-called paper condensers are made u p of alternate sheets of paper and metal foil,

or of paper on which a thin coating of metal has been deposited. The sheets may be either rolled or stacked.

In the higher grade condensers, especially those for use in telephone work, the sheets are either rolled or stacked and are then 1mpregnated with a substance which is both an insulator and a moisture repellent. The resulting unit is then placed in a container, usually of metal, and the empty spaces 1n the container filled with a sealing compound. The condenser terminals are brought out through-the sealing compound and prepared for connection to an external circuit.

Paraifin has been used as an impregnating enter between the layers of the condenser.

This diminishes the insulation resistance of the condensers and decreases its breakdown value. Furthermore in the case of condensers where a very high degree of precision is required the use of paraiiin as an impregnating compound is sometimes unsatisfactory since condensers so impregnated may have as much as 3% lower capacity at 90 F. than at 7 0 F. and with increasing temperature rise the decrease is even more rapid.

An 'object of this invention is a condenser having a practically constant temperaturecapacity characteristic, a high insulation resistance,'and long life. A further object is a condenser having the above characteristics and which is small in size and inexpensive to manufacture.

Such a condenser is attained through the use of a mixture of petrolatum and mineral beeswax. This mixture may be used for both impregnating and filling. Petrolatum, or vaseline, is well known and needs no description; the mineral beeswax may be described as a saturated non-crystalline petroleum product wax having a melting point between 150 F. and 160 F.

Although, somewhat 'similar in appearance to paraiin wax, mineral beeswax, differs from paraliin both in taining small amountsof hardeners, such as `carnauba wax) V1s very satlsfactory. Condensers impregnated and filled with this vcompound do not develop fine cracks when subjected to low temperatures, and in certain cases after impregnation with the above substance, the filling or sealing compound may be omitted.4 This results in a saving not only of cost but what'in some cases is more important, a saving in space.

It has been found that a container impregnated with 75% beeswax will have an insulation resistance of ten times that of a paraffin and carnauba wax impregnated condenser when both are used without the filling compound.

A rolled paper condenser of the type' to which this invention relates is shown on the attached drawing. The sheets of foil and and on this account is4 petrolatum and 25% mineral i of fluidity permispaper or other insulation are-formed into a roll 3 and provided withterminals 4 and 5. This roll is impregnated with amixture, for example of petrolatum and 25% mineral beeswax and is then placed in a container 6 preferably of metal.l The spaces remaining between the roll and container are filled with the impregnating mixture. illustrated is capped with the metal cover 7 and no additional sealing compound isv required. In certain cases a small space may be left at the top and a special sealing compound used in place of the mtal cover.

Since condensers of the type described may be subjected to comparatively high temperatures, it is of importance that the impregnating compound has a melting pointy not less The condenser arrived at byl adding mineral beeswax or a substance of similar properties -to petrolatum until'the desired conditlon is attained. Not

only is the insulation of a condenser so im-v pregnated greatly improved, but the electric capacity of the condenser remains more nearly constant with change in temperature. This characteristic, i. e. the constancy of the capacity, is greater with increasing amounts of mineral beeswax. For the attainment of the highest degree of constancy of capacity with'varying temperatures it has been found that the usual type of paper and tin foil condenser unit should be impregnated with a mixture of petrolatum and mineral beeswax or its equivalent, having about 5% carnaubav wax added.

Exact proportions for the attainment of the most constant value of electric capacity may be determined by consideration of the details 'of the variation of the electrical ca- -pacitj of a condenser. Thus, before impreg .ation, it is found that the electric capacity increases almost uniformly with rise in temperature. When mineral beeswax alone is used for impregnation, its effect is like that of paraffin, namely, to lower the capacity of the condenser with rise in temperature. This effect of the mineral beeswax more than counteracts the tendency of the paper to raise the capacity with rise in temperature over the usual temperature range found in telephone` practice. Petrolatum has the same effect on the condenser capacity as lmineral beeswax, namely, it lowers the capacity with increasing temperature. Carnauba wax on the other hand, is similar in effect to paper and when added to the mineral beeswax or a mixture of mineral beeswax and petrolatum, it increases the capacity of the condenser as the temperature is increased. In general the addition of only a small amount` of carnauba wax, for example, about 5%, is sufiicient to offset the excess capacity lowering effect of the mineral beeswax and petrolatum mixture. It is therefore possible to obtain a mixture of the proper proportions of petrolatum, mineral beeswax or its equivalent and carnauba wax, which when used as an impregnating compound will produce a condenser the capacity of which will remain substantially constant when subjected to temperature variations normally met in practice. i

What is claimed is:

1. An electrical condenser comprising a container enclosing layers of metal foil and paper and van impregnating and filling mixture containing petrolatum and mineral beeswax.

2. An electricalcondenser comprising alternatel layers of metal foil and paperg'said paper being impregnated with a mixture containing petrolatum and mineral beeswax.

3. An electrical condenser comprising a container enclosing layers of metal foil and paper, and an impregnating and filling mixture containing petrolatum, mineral beeswax and a small amount of carnauba wax.

4. .An electrical condenser comprising a container enclosing layers of metal foil and paper 'and an impregnating and filling mixture'4 containing 70%-7 5% petrolatum, 20%-25% of mineral beeswax and 5%-10% carnauba Wax.

5. In a paper-metal foil condenser, an impregnating mixture having as two of its constituents carnauba wax and mineral beeswax in such proportions that the temperature capacity characteristic is substantially constant.

6. In a paper-metal foil condenser, an impregnating mixture consisting of petrolatum, carnauba wax and mineral beeswax in such proportions that the temperature capacity characteristic of the condenser is substantially constant.

7. An electrical condenser comprising a container enclosing layers of metal foil and paper, and an impregnating and filling mixture containing petrolatum and a saturated non-crystalline petroleum product wax having a melting point between 150 F. and 160 F.

8. An electrical condenser comprising a container enclosing layers of metal foil and paper and an impregnating mixture containing petrolatum and a saturated, non-crystalline wax having a melting point of not less than 150 F.

In witness whereof, I hereunto subscribe my name this 25th day of May, A. D. 1926.

- v ELLERY T. HOCH. 

